To do something utterly disgusting but also required. The expression came about when a guy was sharing a small hotel room with his new girlfriend. After passing a stool in the morning, he discovered that the flush didn't work. Rather than face the embarrassment of letting his new flame witness his morning defecation, he dropped to his knees, grabbed the turd and manually fed it through the u-bend.

when you're hungover as shit after a spending a night drunk as a skunk